This invention relates to latching devices for circuit packs as used in the electronics industry.
In the electronics industry, it is conventional practice to provide shelves in electronic apparatus, the shelves having receiving stations for sliding reception of circuit packs. A circuit pack conventionally comprises at least one circuit board to be received within a shelf, and a faceplate mounted at a front of the circuit board to be seen from outside the shelf with the circuit pack mounted in position. To hold a circuit pack correctly in an operating position in its shelf with a connector at the rear of the circuit board held positively in engagement with a corresponding connector in a back plane, latching devices are used. These latching devices are mounted upon the faceplate of the circuit pack and have latched positions in which they engage into recesses in the shelf when the circuit pack is in its operating position. Each latching device needs to be pivoted out of its latched position for removal of its circuit pack, movement out of the latched position also serving to provide leverage to the latching device for urging the circuit pack forwards out of its operating position.
There is a problem which presents itself in cases where electrical cables are required at the fronts of shelves for connection to electrical connectors facing forwardly from the circuit packs. In these cases, difficulty has been found in positional control of the cables which tend to extend haphazardly across the fronts of circuit packs other than the individual packs which the cables actually serve. Hence, in at least some positions along a shelf, in order to remove a circuit pack, the haphazardly placed cables need to be flexed aside from the path of movement of the circuit pack to enable it to be removed from its shelf. Later insertion of a circuit pack then again requires flexing of cables out of the path of the circuit pack. These cable movements serve to unduly stress cable which may eventually result in damage occurring to the cable. The cable movement may be tedious and difficult to perform if cables are to be kept out of contact with a circuit pack during its removal and insertion into a shelf.
In addition, in certain situations, e.g. when circuit packs are held in shelves at central offices, security of electronic equipment may not be a consideration and restrictions need not be placed upon freedom for any person to remove from and insert circuit packs into the shelves. However, should security requirements be necessary, e.g. when installed in customers"" premises, it is not unusual to render a latching device immovable when in its latched position so as to prevent circuit pack removal by unauthorized persons. Latching devices are normally rendered immovable by the use of securing members such as quick release pins or screws which are secured to the faceplates.
The above use of securing members also lessens the possibility of removal of a circuit pack from its shelf in error. In cases of such use, it is considered that error in circuit pack removal is less likely to occur if personnel are required to release a securing member before a latching device can possibly be moved out of its latched position. This is because to release the securing member provides more time for the person performing this function to realize that a mistake is being made. Securing members conventionally extend through securing member receiving orifices defined through the latching devices.
In certain other circuit pack constructions it is desirable to remove faceplates from their circuit boards while the circuit boards remain in their operating positions in shelves. This enables test connectors to be reached at the fronts of the shelves for test purposes during operating conditions of the circuit boards. These faceplates are normally secured by securing members to faceplate mounts of the circuit packs so as to allow for complete removal of the circuit packs commenced by movement of the latching devices out of the latched positions, as discussed above. To allow a faceplate to be removed conveniently from its faceplate mount when in the shelf, the securing members may be reached through access orifices provided in the latching devices. Removal of these securing members then permits faceplate withdrawal from its mount during normal pivoting of the latching devices out of their latched positions.
To provide for all the requirements of the above constructions, some latching devices are required without the necessary apertures, i.e. when there are no security requirements relating to circuit pack removal; other latching devices are required with apertures for security reasons or faceplate removal. Normally, latching devices are made from die cast metal parts at inordinate expense particularly when some, but not all, of these devices are required with apertures. Apart from requiring therefore two different structures of latching device, the apertures need to be machine made which is an expensive procedure.
The present invention seeks to overcome or minimize the above discussed problems.
According to one aspect of the present invention, a latching device is provided having an operating lever having means for pivotally mounting the device to a faceplate, the operating lever extending generally in a radial direction relative to the axis of the pivotal mounting means, and a cable retainer provided upon the lever to direct cable in a radial direction relative to the axis of the pivotal mounting means.
The above latching device according to the invention, when assembled to a faceplate has its operating lever extending longitudinally of the faceplate. Hence, cable provided at the front of the shelf is directionally and positionally controlled by the retainer to extend longitudinally in front of its faceplate to a connector extending forwardly of its circuit pack. The cable does not lie in front of or extend across other circuit packs. It follows that such cable does not need to be flexed to allow for removal of any other circuit pack from its operating position within a shelf whereby the cable requires to be moved only prior to removal of its own circuit pack. Further to this, the cable positioned within the cable retainer inhibits movement of the latching device out of a latched position upon the faceplate. Thus, the person proceeding to remove a circuit pack from its operating position within the shelf, needs firstly to deal with removal of the cable from the retainer, and thus has an extended time in which to contemplate whether he is in fact removing an incorrect circuit pack. It follows, therefore, that with the use of the cable retainer on the latching device, mistakes in removing incorrect circuit packs should be minimized.
In a latching device according to the invention the cable retainer may be formed integrally with the operating lever. Preferably however, the cable retainer is held by a mounting means to the operating lever as the resultant two part construction is simpler to manufacture than an integral one. The mounting means conveniently may comprise latch elements and latch engaging surface elements provided upon the operating lever and upon the cable retainer.
The invention also includes an arrangement of elongate faceplate and latching device in which the latching device is according to the invention as discussed above.
According to a further aspect of the invention there is provided in combination a latching device comprising an operating lever formed with an orifice extending through the lever from front to rear and a plurality of covers which are visually differentiated from one another, the covers being alternatively selectable for mounting in predetermined location upon the front of and covering at least part of the operating lever. At least one of the covers has an orifice provided in a specific position whereby the orifice of this particular cover is aligned with the orifice of the operating lever when the cover is mounted in the predetermined location. At least one other cover is devoid of an orifice provided at the specific location whereby when this particular cover is mounted in the predetermined location, it extends across and obscures the orifice of the operating lever. For mounting purposes, the lever is preferably provided with at least one register for registration of a selected cover to position it in its predetermined location.
Preferably, there are two groups of the covers. In a first of the groups, each cover is formed with an orifice while in the second group, the covers have no such orifices. The orifice in the operating lever is provided, in one arrangement of the inventive combination, to receive a lever securing member which is secured to a faceplate carrying the latching device so as to hold the latching device in a latched position. In another arrangement of the combination, the latching device is to be mounted upon a circuit pack in which the faceplate is removable while the remainder of the pack is retained its operating position in a shelf. In this latter arrangement, the orifice in the operating lever provides access to a securing member which holds the faceplate to its faceplate mount.
In either of the above two arrangements involving the use of securing members, a desired cover of the first group, i.e. with its own individual orifice is mounted upon the operating lever with its orifice aligned with the orifice in the operating lever also to provide access to the locking member. In another arrangement, however, in which no security is required for a circuit pack, then no securing member is used and the selected cover is chosen from the second group of covers. Thus, when this selected cover is placed in its predetermined location upon the operating lever, it conveniently covers the orifice in the operating lever as viewed from the front of the shelf. This provides a more pleasing appearance.
Where a plurality of covers are formed with orifices, then these particular covers are themselves visually distinguished from one another so as to indicate specific functions of circuit packs. The visually differentiating features may be provided in any desirable manner such as by the use of colors, symbols, indicia, shapes, configurations or letters, or combinations thereof. Preferably, these covers are individually distinguished by nomenclature, number, or letter notations, specifically to the use of circuit packs. Where a plurality of covers are provided without orifices, the above comments regarding differentiating features also apply.
Conveniently, covers are substantially planar in form so that they may be cut easily from sheet material or may be easily molded; the distinguishing features are subsequently printed thereon.
It follows from the inventive combination, that a single design of latching device is usable with each of the three possible situations discussed, i.e. for non-security and security situations and the further situation in which a faceplate is required to be removed. The covers serve alternatively to cover or leave access to the aperture in the latching device, as required for each of these above situations, while also providing the required information concerning the use of particular circuit packs. Further advantage is obtained in the inventive combination when the latching device, and preferably also the covers, are made from a suitable plastics material, e.g. a polycarbonate material. With use of planar covers, particularly, this serves to minimize cost especially when using plastics materials.
In a further preferred arrangement of the combination, a cover is provided which is a cable retainer for attachment to the operating lever. A plurality of visually differentiated labels are provided for selection of a suitable label for attachment to the cable retainer to provide information concerning the uses of circuit packs.